Fuel composition



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FUEL CQIVTPOSITI ON Bertrand W. Greenwald, Haddonfield, N. J., assignor to "Cities Service Research and DevelopmentCompany,

New York, N, Y., a corporation of New Jersey No Drawing; Application April 19,1957

' Serial No. 7

United St tes Patent at n ed J ly .15.

2i 2-ethy1 butyl. In the foregoing generic structure, it is, of course, understood that a mixed alkyl tetraesteris contemplated in'which the various radicalsrnay be of like or unlike lconfiguration, depending on the source ofltheacid. e a

The additives of the present invention may be prepared in any suitable manner. For "example, "theitetra alkyl esters may be prepared according to the methoddescribed This invention relates to hydrocarbon compositions Y it'ed motor fuel compositions. f V I g V t The increasing refinements of motor'fuels required by More particularly this invention relates to oxidation inhib engines of improved design and operatin'gefliciency require" of petroleum refiners continuous improvement in gasoline quality. These improvements are evidenced by continuously increasing octane-'values, increase'd heat stability, lower carbon deposit, lower impurity content, improved color stabilization; improved low temperature operating efiiciency, and increased oxidation inhibiting characteristics. t v t It is with this latter property of motor fuel composi- 'tions that this invention is particularly concerned.

. It has been accepted practice in the petroleum industry for many years toadd to motor fuel compositions a fsmall amount of 'a corrosion inhibiting additive to minimize the corrosiveness of the fuel composition. lThese. additives must be comparatively inexpensive, and simultaneously inhibit corrosion without adversely affecting theburning qualities of the motor fuel. I

It is accordingly an object of the present invention to provide a motor fuel composition having improved oxidal tion'inhibiting characteristics. a

It is another object of the present invention to provide, an improved gasoline composition ofreduced corrosive characteristics.

The foregoing objects are attained according to the present invention by incorporating in the fuel composition as a corrosion inhibitor alkyl esters of 1,2,3,4 butane tetracarboxylic acid. .These esters can be conveniently represented by the following formula:

CH2-O 0 o R oH-o o o R -wherein R, R, R", and Rf represent alkyl radicals having from 1 to 8 carbon atoms in a straight or branched;

chain configuration' These groups are preferably satin rated, and'include such radicals as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, famyl, f2-ethyl1hexyl, and

'furth rldistilled. a.

infU. s; 2,687,429 in which 1 11101 or a' dialkyl fllfilalate is combined with l'mol of a {dialkyl succinate. When preparedaccording to this "method, it is relatively easy to reactant mixture 'is' conducted at a suitable temperature,

depending on the particular solvent used, fora period of from 4 to 8 hours. Generally speaking, for the solvents heretofore mentioned, refluxwill be conducted, attemperatures Iangingifrom about'80 C. to about 140 C.

After the. theoreticalamount 'of water has 'beencol lected, indicating completion of the esterification reaction, the; solyent is, distilledxfrom thereaction zone, leaving a crude pester, product which in itself can be satisfactorily used as c luadditive for the purposes of'this invention. It is preferred, however, toobtain a purified product. Accordingly, the crude ester product is washed and The ttittiestersprepared according to the foregoing rea tion are the, unique property of providing anti-oxidant 3 I characteri tics for, motor fuel composition when" used in comparatively small amounts.

The following is an'exam'ple of the preparation of a V typical tetraalkyl ester utilized in the present invention.

Ina 1 liter three-neck flask fitted with a water trap, stirrer and condenser, /2 mol of butane tetracarboxylic acid (117 grams dry) was dissolved in 3 mols of Z-ethyl butyl alcohol in the presence of 100 ml. of toluene. This reactant mixture was refluxed for a period of 7 hours,

after which the volume of azeotropewater collected was between 62 and 65 ml.. The theoretical amount of water (including the water present in the acid) should have been .t .n 1l.: Recovery data and significant physical and chemical propertiesf'ofi the reaction product are shown in TableI which follows. The product'of the foregoing example is identified as D in the table. Included'in the tablejin addition to the, 2f-ethyl butyl tetraester, is a series o e te P e a ed in a similar manner to that previously described, a

TABLE I Yields and properties of'buzan'e tetracarbobcylic acid esters A B O D E Alcohol Uses in Esterificatmn; e

- I n-propyl n-butyl n-amyl Z-ethyl- 2ethylp butyl hexyl Percent Yield of Crude Ester.. 78

- Appearance and Golqr ofyDlst lled 1 p "Estera Neut. N0. Distilled Ester 198 Sap. N0. (ASTMyDistilled Ester... Sap. N0. (Diethylene Glycol-Phone tole'M if Ester N0. of DlstilledEster yEst'er Np.; (Theor.)'ot Pur Tetraesters. V

As described above, the tetra alkyl esters of 1,2,3,4 butane carboxylic acid find particular application as oxidation inhibitors for gasoline compositions. Generally speaking, the alkyl esters of the present invention may be used for the oxidation inhibition of any gasoline composition. Specifically, they may be used in unsaturated gasoline, polymerized gasoline, reformed gasoline, cracked gasoline and aviation gasoline. In addition to the specific gasoline compositions mentioned, these additives may also be used in other hydrocarbon fuel compositions such as fuel oil and diesel oil.

The additive of the present invention is generally added to the fuel composition in an amount of less than 1% by weight, and more generally in the range of from about 0.000l% to about 1% by weight, and preferably from about 0.001% to about 0.1%.

The additives of the present invention may be used if desired along with other additives such as metal deactivators, dyes, anti-knock agents, upper cylinder lubricants, heat stabilizers, gum inhibitors, and the like.

To demonstrate the effectiveness of the corrosion inhibitors of the present invention in reducing the oxidation or corrosion tendencies of gasoline compositions, a series of tests were carried out in which gasoline compositions were prepared with varying weight amounts of the additives previously described. In carrying out these tests, a gasoline generally referred to is regular grade. This gasoline had the following properties and characteristics:

Research octane (F-l) min 90.0

Motor octane (1 2) min 82.0

Distillation:

10% evap. temp. F. max 140 50% evap. temp. F. max 245 90% evap. temp. F. max 380 End point F. max 425 Residue percent max 2.0 R. V. P. at 100 F. max 10.0 Gum A. S. T. M. max 4.0 Gum F. S. B. 330.1 max 20.0 Sulfur wt. percent max 0.10

The test used in determining the eflfectiveness of these agents as oxidation inhibitors in a fuel composition was the modified A. S. T. M. turbine oil test D665-52T modified to room temperature on a four hour cycle using synthetic sea water prepared according to Army Specification 2-126. The test equipment included a series of 400 ml. beakers provided with a plastic cover and a stirrer inserted therein. The test was carried out on metal test strips 4" x l x %'f of cold rolled open hearth 1018 steel polished with a final grit size of 180. In carrying out a test the panel or test strip is cleaned with acid and weighed after polishing and emerged in the solution being tested. About three inches of the test strip is placed in the solution. The stirrers are run at about 50 R. P. M. during the period of test. Samples of gasoline containing the specified amount of additive as shown in the tables which follow were added to the beakers to provide a total test sample of about 300 ml. of the gasoline composition.

After immersion in the gasoline solution for about four hours, the panels are removed, cleaned, and weighed to determine weight loss. The weight loss in grams expressed inthe tables which follow and the exposed area of the panel are used in calculating the corrosion rate in inches per year according to the following formula:

Wt. loss (g) Area X (0.683) =orros1on rate, Inches/year (Navy Department Specification 51-1 11, May lj, 1 945 J In applying the above formula, the area is determined by measuring from'the bottom of the test strip to the corrosion line formed at the interface of the liquid and vapor phases. The area is then calculated in square inches, with proper consideration being given to the sides and edges of the test strip.

In Table II below, results are provided measuring the oxidation characteristics of a gasoline containing the normal butyl tetraester of butane carboxylic acid. The test was carried out in the manner described above.

TABLE II Wt. Change Corrosion Ester (B) P. p. m of Panel rate, inohes/ (gm) y In the results reported in Table II, it will be noted that substantial reduction in the corrosive effect of the gasoline composition was obtained by including in the gasoline a small amount of ester B. It will be evident that the additives of the present invention provided a considerable reduction in the corrosive characteristics of the gasoline. V

In a similar manner, the normal amyl ester of butane tetracarboxylic acid (compound C, Table I) was tested by being added to gasoline in the amount specified. The results of this test are noted in Table III, below.

TABLE III Wt. Change Corrosion Ester (C) P. p. In of Panel rate, inches/ (gm.) year In the foregoing table, results of the corrosion inhibiting properties of a commercially available additive are compared with the results obtained with the normal amyl tetraester of butane carboxylic acid. It will be noted that at 50 p. p. m. the crude or distilled ester of the present invention was more effective than the commercial additive. In all respects, with the possible exception of the crude ester in the amount of 10 p. p. m., substantial improvement in corrosion inhibition was obtained by the presence of the additives of the present invention.

In a manner similar to the test method described in connection with Tables II and III above, the Z-ethyi butyl ester of butane tetracarboxylic acicl (compound D, Table I) was added to a cracked gasoline in the amount stated. The corrosion test results for gasolines with and without this additive are reported in Table IV.

Here again it will be noted, as with Tables II and III, that the inhibitors of the present invention provide substantial protection of the metal strips in gasoline compositions, particularly when compared with the blank, or in'this case with commercially available corrosion inhibiting additives identified as A and C. A further test was carried out with the 2-ethy1 hexyl ester of butane tetracarboxylic acid in which 50 p. p. m. of the additive were added to a cracked gasoline having the' properties previously described. The results of this test are as follows:

The results noted above, in which ester E was compared with commercial Bryton calcium sulfate additive at 50 p. p. m., clearly show the superiority of the additives of this invention over the commercially available and presently used additives.

Although the present invention has been described in conjunction with certain preferred embodiments thereof, those skilled in the art will recognize that certain variations and modifications can be made hereto. Such modifications are to be considered within the scope of this specification and the claims appended hereto.

- What I claim as my invention and desire to secure by Letters Patent of the United States is:

1. A gasoline fuel containing from 0.002 to about 1.0% based on the weight of the gasoline fuel of an alkyl tetraester having the formula I OHz-VCOOR' V wherein R, R, R", and R represent alkyl substituents having from 1 to 6 carbon atoms.

2. A gasoline fuel as claimed in claim 1, wherein R, R', R", and R have a like number of carbon atoms.

3. A gasoline fuel as claimed in claim 1, wherein R, R, R", and R have a differing number of carbon atoms. 7

4. A gasoline as claimed in claim 1, wherein R, R, R", and R'- are n-butyl substituents.

5. A gasoline as claimed in claim 1, wherein R, R,

R", and R are n-amyl substituents.

6. A gasoline as claimed in claim 1, wherein R, R,

R, and R are 2-ethyl hexyl substituents.

References Cited in the file of this patent UNITED STATES PATENTS 1,995,615 Jaeger Mar. 26, 1935.

2,204,598 Humphreys et al June 18, 1940 2,497,432 Blake Feb. 14, 1950 2,687,429 Dazzi Aug. 24, 1 954 FOREIGN PATENTS I r 749,505 Great Britain May 30,1956 

1. A GASOLINE FUEL CONTAINING FROM 0.002 TO ABOUT 1.0% BASED ON THE WEIGHT OF THE GASOLINE FUEL OF AN ALKYL TETRAESTER HAVING THE FORMULA 